Container suitable for dropping from aircraft and the like



Dem 1948- E. R. CAMPBELL ETAL 2,457,205

CONTAINER SUITABLE FOR DROPPING FROM AIRCRAFT AND THE LIKE Filed June 14, 1944 2 Sheets-Sheet 1 Dec. 28, 1948. RHCAMPBELL I 2,457,205

CONTAINER SUITABLE FOR DROPPING FROM AIRCRAFT AND THE LIKE Filed June 14, 1944 2 Sheets-Sheet 2 Patented Dec. 28, 1948 CONTAINER SUITABLE FOR DROPPING FnoM AIRCRAFT AND THE LIKE Edward Ralph Campbell, Ivanhoe, Kenneth Moreton Frewin, .Elsternwick, .Frank Wentwor th 'Lennox, Toorak, and Rowland Price Morris, NorthBrighton, Victoria-Australia, as-

signors to Air Supply Packs Proprietary Limited, Melbourne, Victoria, Australia Application June .14, 1944, Serial-No. 540 328. I

.In Australia June 21, 19.43

- 1 This invention relates to improvements in containers suitable .for dropping from aircraft and the like, and has been devised primarily to facilitate the dropping of food, ammunition and other supplies to ground troops'and other personnel'in localities which are otherwise difiicult of access, but'is not limited'thereto.

The dropping of supplies including weapons and ammunition is an important factor in modern warfare particularly islandwarfare and the containers heretofore used for this purpose have, we believe, been relatively unsatisfactory chiefly for the reason that they did not sufiiciently protect their contents from the shock of impactwith the ground, though they have also been subject to other disadvantages. 7

Now, the general object of this'invention is to provide an improved container for the purpose described which will better protect the contents upon impact with the ground or'water and which provides additional advantages some of which are hereinafter described.

One broad feature of the invention resides in a container comprising a plurality of coaxially arranged units including a deformable percussion member and a storage compartment and means detachably securing said coaxially arranged'units together, said'percussion member containing at least one air compression compartment. The container may be of any desired cross-sectional shape-e. g. circular-or rectangular, and the said air compression compartment is preferably sealed.

Another feature of the invention resides in the provision at the end of the container opposite to-the percussion member of a housing for a packed parachute. This parachute housing may have a readily removable cover capable of serving as apilot parachute for the main parachute.

Still another feature of the invention resides in detachably securing together the tubular units forming the body of the container by means of one or more flexible members extending longitudinally of the container and attached to the upperand lower units thereof. For this purpose a'cord is preferably passed-backwards and forwards-'externally-of the container, such cord being suitably "attached to grummets or the like on the upper and'lower units of the device the upper grummets being also connected to the shroud lines: of the parachute.

The aforesaid percussion member at the lower tubular units forming the body of -the container 13 Claims. (Cl. 244-138) 2 and aforesaid cap or cover at the upper end thereof. I

The saidpercussion member may be provided intermediate its vends with a weakened annulus to facilitate crumpling thereof and ensure that ultimate failure of this member will occur'insucha manner asto afford the best protection toth'e contents of the container.

Still another feature of the invention resides in the provision in the body of the container of one or-more'transverse diaphragms which are slidab-le longitudinally"therein in close contact with the wall thereof such diarfl h'agrns serving not onlyas partitions for separating difierent kinds of articlesybu't also as pistons which, by compressing-the-air therebelow, provide an additional shock absorbing action.

The-container-is preferablywater-tigm toprotect the contents and, when loaded, preferably contains suffi'cient air space to enableit to float in water.

Other features of the invention will appear from the following more particular description. In the drawings; I

Figure 1 is a view in sectional elevation showing the preferred form -of-container in accordance With'the invention,

Figure 2 is a view in sectional elevation showing the outerseries of component parts of the con-- tainer.

Figure 3is a view simila'r to Figure 2 andshows the inner series of component parts.

Figure 4 is a view in planet the container.

Figure 5" is a fragmentary sectional viewto' a largerscale and showsdetails of 'construction of elevation of a suspension ring.' Y

' Figure 11 is a, view-in section ofthe upper part of the parachute bucket and shows an alternative cover therefor,

"Figures '12 andlB: are views in elevation and verticalsection respectively of asuspension band.

. Figure 141s aview-partly insection'and partly in elevation and shows a method of assembling the container for transport when empty.

Figures and 16 are fragmentary views in cross section show'ingalternative methods of lacing the parachute bucket and/or percussion nose; and

Figures 17 and 18 are sectional views showing modifications in the construction of the percussion nose.

Referring now to Figure l of the drawings, the

sists of a plurality of inner and outer tubes each i V of which is preferably formed of multi-ply paper that is to say, each tube is formed by Winding a continuous strip of paper on a former until the required thickness is produced, the various oonvolutions beingadhesively secured together. For the purpose under consideration each tube requires to be of substantial thickness-e. g. threesixteenths of an inch. All of the tubes are preferably impregnated as with wax to render them waterproof while additionally the outer surfaces are preferably coated with shellac, paint or other approved material,

In lieu of forming the tubes of multi-ply paper, they maybe moulded from paper fibre which may, if desired, be impregnated with a, synthetic resin. Likewise other alternative materials may be used.

More particularly the body comprises a main outer tube l3 which slidably encloses two coaxially arranged inner tubes 14 and I5 which,together, are-equal in length to the outer tube l3 (see Fig ures2and3).

When assembled in the container the inner tube l5 projects somewhat from the lower end of the outer tube I3 to form a spigot which is received in the upper end of the percussion nose II. -A distance ring i5 is arranged within the lower. end of the tube l5 and its upper endforms a shoulder on which is supported a sealing disc I5 which is secured and sealed in position in any suitable way whereby the contentsof the container, which are packed into the space above the disc I5 will be protected should the container be droppedin water. The upper end ofthe inner tube I4 is disposed below the top of the tube I3,:thereby permitting the lower end portion of a further inner tube [6 to project into the upper portion of. the body tube 13.

A further outer tube i1 is fitted over the tube 16 whereby its lower end engages the upper end of the tube 13. The tubes [6 and I! together form an extensionpiece which is used when it is desired to form a container of greater capacity than the body tube 13. It will likewise be evident that any desired number of additional extension pieces may be employed in the same manner as required for particular circumstances.

Arranged within the upper end of the outer extension tube 11 and resting on the upper end of the inner. tube I6 is a distance ring 18 the upper end of whichformsa shoulder on which a sealing disc I9 is seated some distance below the top of the tube H, such disc being formed of waxed chipboard or other approved material and being suitably sealed in position in a watertight manner.

The lower end of the parachute bucket I2 is received neatly within the upper end of the extension tube H (or within the main body tube end rests upon the peripheral portion of the sealing disc 19.

The parachute bucket I2 is of composite construction and comprises an impregnated main tube [2 formed of suitable material such as multi-ply paper provided externally at its lower end with an external reinforcing ring l2 which may be of similar material, this ring being suitably secured in position such as by screws or rivets and adhesive material (Figure 6).

Likewise coaxially arranged rings f2 and I2 are secured within the lower end of the tube l2, the adjacent ends of these inner rings being spaced apart to form a circumferential recess in which the peripheral portion of a transverse strengthening disc I2 is located, such disc also being formed of waxed chipboard or the like and serving to prevent collapse of the bucket when the parachute opens.

A further disc [2 provided at its center with a relatively large hole i2 rests at its periphery on the upper end of the ring l2 and forms the bottom of a compartment in which a folded parachute I9 is housed. The outer end of this compartment is normally closed by a known type of cover 20 formed of canvas or other suitable flexible material such cover comprising a plurality of flaps the free ends of which overlap at the axis of the container and are detachably connected together by suitable fastening means (not shown).

A cord 2| is attached to the top of the parachute by a breaking link (not shown) and in use its free end is fixed to the aircraft on which the device is carried whereby, when the container is dropped from the aircraft, the cord becomes taut and the parachute is pulled from the parachute bucket at the same time releasing the flaps of the canvas cover 28. The breaking link subsequently breaks in the usual way.

The shroud lines 22 of the parachute are connected to a suspension ring 23 (Figure 10) which is conveniently formed of metal, such ring normally resting on the top of the disc I2 in the parachute bucket, and extending through the central hole in the superposed disc l2 as shown in Figure l.

The suspension ring 23 is preferably provided with a central cross bar 23' which prevents lateral collapse thereof when it is subjected to the shock of the opening of the parachute and which additionally separates the shroud lines 22 from a cord 24 by which the ring is secured to the parachute bucket such cord being arranged as hereinafter described. The cross bar 23' thus also prevents fouling of the shroud lines with the cord 24.

A plurality of closely spaced pairs of circumferentially arranged holes I2 are formed in the lower part of the parachute bucket l2 and such holes extend through the main tube i2, the outer reinforcing ring i2 and the inner ring r2 as best shown in Figures 8 and 9. The latter figure shows 11 pairs of such holes though a lower odd number-e. g. 7may be provided in order to reduce the length of cords and the time of lacing. While it is not essential to provide an odd number of pairs of holes, an odd number is advantageous when the cord 24 is laced in the preferred manner shown in Figure 9. Thus one end of the cord is passed through one of the pair of holes at the position designated I, then through the lower half of the suspension ring 23 to and through one of the holes at position II. The cord is then feiurned through the other hole at position II leaving an i exposed loop :24 and .is then passed again thr-ough thelower half of the .suspension ringand so on,;to and through eachlpairi of holes in the-order indicated by the romannumerals until. an external 'loop 24' is arranged :between the'holes formingeach pair. Finallythe free ends of the cord are tied as vshowntat 242 inside the parachute bucket it being understood'that thecord passes-through .the lower half of the suspensionring at eachitraverse of the'interiorconstruction and comprises an outertubel I. the

upper end of l which abuts against the lower end of .thebody'tube l3. and which is correctlypositioned by the aforesaid :projecting lower end 'of the inner tube l5. Attached to the lower end of thetube I l is aconical nosepiece l the upper end of which is formed with a short integral cylindrical extension which fits neatly within saidouter tube H.

The cone may convenientlybeformed b'y sue cessively placing single ply paper cones over a formeruntil the :required thickness is builtup. theijoints in the various constituent cones being staggered .and the-constituent gcones being'adhesively secured together. Finally the composite cone is consolidated in a suitable press.

'.The.nosepiece ispermanently secured tothe tube 1'! in any suitable way such as by screws or--r-i-vetsand an adhesive composition.

.A diaphragm-disc H isarranged within the nosepiece atthe upper-end of the conical portion' thereof such disc being retained in position by a spacing ringl l athe upper .endof which forms an annular seating for'qa further diaphragm disc .1! l which is suitablyfsecured in position. Thus=the disc I I dividesthe space below the'disc H into two sealed air compartments (seeFiguIfe 5).

A sealing disc 301s mounted-on theshoulder formed by the upper end of the cylindrical upper portion of the nosepiece'and is, suitably sealed thereto and the lower end of the' tube l5, abuts thereagainst when the container is. assembled (seeFigures 1 and 5).

Aishock-absorbing pad disc 3! which fitsneatly within the tube l'5 preferablyrests on thetofpxo'f the disc .30 inthe'nosepiece immediately below the said sealing disc- 5 the function of thispad being-to absorb shock and thereby assist in preventing damage to the contents when the 'container strikes the ground or waten shown in.-Figure.7-. thepad disc may consist of upper'and' lower chipboard discs having their edges enclosed within a ring of similar material the. in; teriorof the disc; being filled with sawdust 3|", sponge or crepe rubber or other suitable material.

A plurality of circumferentiallyarranged pairs ofclosely spaced holes l-l cor-responding inynum her to theholes I? in the parachute bucket are,

formedinthe wall of the percussion nose All somewhatabove the diaphragm disc H A cord ;25 isthreaded' throughthesepairsof holes .in. the manner previously described :with

reference to the parachute bucket whereby a.

plurality of. projecting loops 25 is .formed,

thoughinthis case the cords do not extend through any-member corresponding to'thessuspension ring 23 in the parachute r bucket.

throughythe {projecting loops .124 'and .25 inithe:

manner shown in Figure 8-thatis tosay; the:;tie

cord zfiismassed backwards and forwardsalong thevcontainer-and1through theloops at'the'same time progressing around thecontainer. Finally, when the cord ispulled tight, the free endsare tied together as'indicatedat 26.

Thus, .when'the container is launched. from an;

aircraft as previously described and the parachute opens; the containeris supported :by the suspensionring zii and the cords 24, $26 and, 25. sothatthe units of the container are securely held-together and the Weight thereof is evenly distributed.

.Inorderztoreducezthe length of the tie cordf26- and the time of lacing, thesaid cord may be passed :through adjacent'pairs of loops 24 and 25. aas indicated in broken lines in Figure 8, the loops .Zd'xand 25 being then preferably longer assliowntoreduce the lateral component ofv the pressure, exertedv thereby on the parachute bucket.

Analternative method of lacing the cords .24

is;indicated in Figure 15 in which theparachute bucket is provided with a circumferential. series oftevenly spaced holes and the cord 2 3 passes twice through each hole to form the external loop'sa24'. Each external loop is preferably fitted number ofholes is provided and the cord .25-is.

replaced. by a series of. gIummetsZB consisting of :endless cords. The doubled ends of each grumrnet arecpassedzthrough a diametricallyopposed pair. of holes to form external loops through-which'the .tie cord 26 is threaded in the manner :already described.

It -wiil beevide'nt however that thecontainer units inay be detachably connected together by any other suitable means in lieu of a tie cord as "255i 'F'orexample, we may emplovra circumferentially arranged series of longitudinally extendingstraps each. fitted with a quick release buckle.

Whenit is desired to carry the con'tainer-inthe bomb rackof an aircraft, it is preferably fitted withoneor moreencircling metal bands 32 (see Figures.1,28, 12.and 13). The ends of this band are connected by a pivoted toggle link 32 which,

when turneddownwardlywagainst the adjacent portion oiuthe band, contracts the latter tightli ablout thebody of th-econtai'ner, the link being then retained in positionby a slidable keeper member 32 This keeper is provided with lugs 32 which, 'whenprcss'cd'down around the end of the alinkBZ', prevent displacement ofxthe said keeper. :A 100 :332 secured to the band enables it to:be attached toth'e bomb rack.

In use the container is loaded with the required materials before the-sealing disc t9 and parachute bucketeare placed; imposition, and, when the .con-

tents are :suitable, "one or more additional pad discsastl or plain discs. of the same size may be inserted at suitable intervals to divide theinterioriinto separatecompartments and to assistxin absorbingth'e-shock.20fimpact. that-even when plain discs are used for this purpose,- a,;icer.tain :degree 20f shock absorbing action is obtained. as theidiscs serve a-spi'st'ons .at the time'of; impactzand compress. the air therebelow.

Thezexternal joints between "the various elements of the container are also renderedwatere It will ice-evident 7 tightin any appropriate way and thus thecon tents are completely sealed and,'if not greatly overloaded, the container will fioat in water.

In use the container is launched from the aircraft in any convenient manner and, when the aforesaid static line becomes tau-t. the parachute is withdrawn from the parachute bucket, the breaking link in the static lin-ebeing broken at or about this time.

The shock produced by the opening of the parachute is partly absorbed by the stretching of the shroud lines thereof and of the container tie cords 24, and 28, while additionally the paper container elements possess a useful measure of resilience and yield when subjected to intense pressure by the cords 24 and 25.

Thus the container supported by the tie cords thereof descends with the percussion nose lowermosti. e. in the attitude shown in Figure 1.

When the nosepiece strikes the ground, it is initially deformed by the force of the impact (see broken lines in Figure l) at the same time compressing the air in the closed compartments thereof: Axial deformation may be ensured by providing a weakened circumferential zone therein, though this has not been found necessary.

Finally the nosepiece bursts and, during deformation and subsequent bursting, a substantial amount of energy is dissipated by compression and release of the air therein whereby the speed of descent of the container is materially reduced. At this stage theeontentsof the container tend to move in advance of the container itself thus stretching the lacing cords and slightly elongating the holes through which they pass. In this way afurther absorption of energy is efiected, and it may here be mentioned that the transverse lacing of the tie cord 25 in the percussion nose provides additional support for the reason that the various traverses do not cross at a point but cover a substantial area. Additional energy is dissipated owing to the resilience of the materials formin the container and the contents are generally found to be in a condition much superior to that experienced with present types of containers known to us.

In order to secure optimum results when the container is dropped on a relatively hard surface, it is important that the percussion nose should burst on impact and, in order to secure this result, it is necessary that the strength of the nose should bear an appropriate relation to the kinetic energy of the container at the time of. impact. The required variation in strength of the percussion nose may be obtained when same is formed of multi-ply paper by variation of the number of plys employed and similar considerations apply when same are otherwise formed.

In some cases therefore it may be necessary to replace a percussion nose on a container with one having a different bursting strength, though this would not ordinarily be necessary as in general the total weight of the container and the diameter of the parachute would not be substantially varied in which case the energy requiring absorption at impact would remain substantially Accordingly it may be advantageousunder some conditions to modify the construction of the per-' ped formation to facilitate crumpling,

It is to be-noted also that it is not essential to provide the percussion nose with an air compartment which is sealed as above described, provided the construction of the percussion member'is such as to permit of compression of air therein and ultimate bursting of the nose. Thus, for example, if the percussion nose were provided at its lower end with a small axial opening, such opening would be sealed by the crumpling of the material at impact and thereafter compression of the enclosed air would occur. Even one or more small openings near the upper end of the air compartment would not prevent a considerable increase in air pressure during the rapid crumpling of the 11058.

Alternatively the air compression compartment may contain sponge rubber or other resilient cellular material providing a multiplicity of air or gas filled cells which may be compressed at impact or the compartment may contain a sealed air filled rubber bag. It will be evident therefore that the air compression compartment does not necessarily constitute a sealed air compartment though this latter construction is preferred.

The construction of the container permits of its being assembled in a relatively compact condition for transport. Thus, as shown in Figure 14, the percussion nose and parachute bucket are reversed whereby these parts project into the hollow body of the container, the various units being retained together by the usual tie cord 26. In this condition, however, it is desirable to protect the then outer ends of the percussion nose and parachute bucket against accidental damage which would militate against the subsequent formation of watertight joints between same and the corresponding ends of the body. For this purpose a composite protector ring 33 is preferably fitted temporarily to the exposed end of the para-' chute bucket may be protected by causing the inner-ring I2 to extend somewhat beyond the end of the main tube 12 as shown in Figures 6 and 14.

It is further to be noted that the larger tubes containers for despatching supplies to forward areas for which purpose they may be fitted with suitable end covers. Likewise these elements and the cords incorporated in the container would often be useful to troops in isolated positions.

In this connection it may in some cases be advantageous (see full lines at the lower right-hand portion of Figure 8), to pass a cord 34 circumfer entially around the container and through each of the loops 2-4 on the parachute bucket, the ends of the cord 34 being then tied together. The tie cord 26 is passed over the cord 34 and around (but not through) each loop 24' as illustrated, a simihr arrangement being provided, if desired, at the' energet c Figure 11 shows 'apara'chute'" bucket provided with an alternativetype of-removable cover -35 such cover-being formed 'of semi rigidmaterial "such as cardboard. The static line, 21 passes outwardly through the center of the cover and "then overthe surface thereof to the'upper en'd of the parachute bucket l2 which it encircles onceas-shown'at 21', this turn being covered by astrip 36 of paperor other rupturable material "which normally retains the cover to the bucket i l l-. The static line is then woundseveral times around a grooved intermediate portion of'the cover as shownat 21 such" turns beingnormally retained in position by the rupturable"coverstrip from which the 'free end of the static line projects. a

When the container is released from'the aircraft, the static lineis 'first'iunwound'atil at the same" time rupturing. the relevant part of the cover strip 36; 'Theturn'at zl' is then unwound; thus breaking thefstripi'afij and releasing the cover fromthebucket. The cover is then pulled from the bucket and, if it is suitably attached to the static line and parachute, it will act as 'a'pil'ot parachute forthe mainparachute.

Among other advantages this type of cover for I additionally various unitary parts are capable of other uses 'both before andafter' the container is dropped The shock absorbing'qualities of the container permit of a higher terminal velocity which in turn enables a relatively small and inexpensive parachute to be used. This is important because of the resultant saving both in materials and labor.

As already indicated, actual tests have shown that the contents are generally recovered in better condition than is usually the case when other known types of containers are used, while finally the container will float if dropped in water so that in many cases it could be recovered with the contents undamaged and may even. serve as a float for life saving purposes in cases of emergency.

The invention is not limited to the use of a percussion nose of conical form, though this shape is preferred. For example, if it is intended to transport the containers on end in an aircraft, they may be provided with fiat ended cylindrical percussion noses.

Again a percussion nose of hemispherical form may be used and would probably operate more satisfactorily in the event of its striking the ground when the longitudinal axis of the container was disposed at a substantial angle to the vertical.

Likewise the percussion nose may be of pyramidal form and would be advantageous if, for example, the body of the container were of square shape in cross section. In this case the body members may be formed so as to permit of their being knocked down for transport in i omn il e ine ubu a unit o aol aid u t b i" fl xib ma er -"p passe "series" thereof; a

the flat and thepercussion nose and parachute 1 bucketwould servei inconjunction with" suitable intermediate stifieningynieang to retain the shape when the" container isassembled.

Itwillalso be evident that a body-of rectangu 'lar-gc ross-sectional shape would in many cases permit ofmqre efiectiv l$ ubeing made of the storage; space.

"(lontainers as described herein may be modifled" to accommodate "anti-personnel, incendiary, time or other typebombs. Thus'the use ofthe "calming is "n s't ie d b he a chi i g o supplies;

. Weepmim;

A'container having a'storage compartment plur y oic a e ly arrang ing a. 'ee u si ntmembs locat de n and 9 wonta n a c cu e al s rie o o s s iin x rna -1y fr paced nits Q1. he on iner: ansi' lon tudin lly fit nd nefi ibl l l ean arrar s f xter Hy o hex ntainer and" ccnneeied t a d 'sr'ad er es f emir te 1. .911 whereby th s idlunii are "detachably'secured'together A. co t ner acs rqiil 'i' w er a d'fle i materiali i iming th .xp iee ine l op x e ds'siibsiaetiei y di me ically acros it.. l

.m. 1: wher in externally 9i. con ain r-and. i ternatelythroueh' icc neloops o at ea t one c the s c n iectegit then;

said ifl xiib ef tie "means extends; ba kw rds n thanroifi Agcont in' r com The a. plur l y Pi 9- axially arranged" 'interfit'ting tubulanu'riits, the unit located at one end being a percussion member and the unit at the opposite end of the container forming a compartment for a folded parachute, a circumferential series of projecting loops of flexible material extending outwardly from each of said end units, longitudinally extending flexible tie means arranged externally of the container and connected to said projecting loops whereby the various units of the container are normally retained together, a folded parachute in said parachute compartment, shroud lines on the parachute, a suspension ring arranged within the parachute compartment and secured to the shroud lines, said suspension ring being additionally connected to the flexible material forming the aforesaid loops on the unit forming the parachute compartment, said percussion member being formed of material having a low tensile strength, low elongation and a relatively high compression strength.

6. A container according to claim 1 wherein said percussion member is of composite construction and comprises a parallel tubular portion secured to and enclosing the upper end of a downwardly converging portion and a transverse partition extending across an upper part of the downwardly converging portion and forming a sealed air compartment therebelow.

7. A container comprising tubular means forming a storage compartment and hollow means of semi-rigid rupturableimaterial located between said storage compartrnent and oneend of the container and forming a sealed air cqlllpartment, said tubular means comprising at least one outer tubular member and at least one inner tubular 5 member slidably mounted within said outer member and being a neat fit therein, the inner tubular member being so disposed relatively to the outer tubular member that a spigot is formed at one end of the storage compartment and a socket is 10 formed at the other end thereof. i

3. A containeraccording to claim 1,.wherein the end unit remote from the percussion member contains a compartment for apacked parachute,

said compartment bein open at its'outer end. .15

9. A percussion head for the purpose described,

comprising a hollow" compression member having an air-compression chamber, said hollow member being constructed of Ta cellulosic material whereby it has a low tensilestrength, low elongation and a relatively high compressive strength, the compression member including an impact terminal adapted to impact stress so that it ..will first crumple and thus increasethe pressureof the air in such compression member. to a point to there- :35

after rupture such member.

' 10. A percussion hea'dg'for the purpose described, comprising a hollow compression memher having an ai'r -,con pression chamber said hollow member being'constructedprincipally oi g paper pulp; whereby it has alow tensile strength,

low elongation and a relatively high compressive strength, the compression niemberincluding an impact terminal adapted to impact stress so that it will first crumple and thus increaseithe pres- 35 sure of the air'in such compression member to a point to thereafter rupture such member.

11. A percussion head' 'for, the purpose described, including" a hollow member, an air compression compartment therein, said hollow memi!) her being constructed principally of cardboard,

whereby it'has a low tensile strength, low elongation, and relatively highcompressive strength, to insure that when the h ollow member is subjected ditions of descent pressure under a predetermined value, such hollow member will first crumple to compressthe air of such air compartment and thereafter rupture under such air compression.

12. A percussion head for the purpose described, comprising a hollow compression head having an air compression chamber, said head being constructed principally of chipboard, whereby it has a low tensile strength, which head when subject to landing impact stresses due to normal conditions of descent pressure above a predetermined valve will be caused first to crumple and thereafterto rupture.

13. Apercussion head for the purpose described, comprising a hollow compression head having an air compression chamber, said head being constructed principally of bonded paper, whereby it has a low tensile strength, which head, when subject to landing impact stresses due to normal conditions of descent pressure above a predetermined value will be caused first to crumple and thereafter to rupture.

EDWARD RALPH CAMPBELL. KENNETH MORETON FREWHV. FRANK WENTWORTH LENNOX. ROWLAND PRICE MORRIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS to landing impact stresses'due tonormal con- 35, A 

